(1) Field of the Invention
The present invention relates to a syntax parser for data in a format defined by MPEG2 (Moving Picture Experts Group 2) for use in a video decoder and, more particularly, to a syntax parser having minimum size and maximum parsing speed by using a micro controller. An embedded micro-controller is used so that micro-instructions for a program may be executed directly without the need for a particular instruction decoder and additional instruction cycles for decoding the instruction.
(2) Description of the Prior Art
MPEG2 is a standard for encoding/decoding video data with high efficiency. MPEG2 can compress a picture of higher quality than television broadcast without visible loss, so it stands out as a basic technique of bandwidth limited applications, such as multimedia and wire/wireless communication.
In general, the process used to decode a compressed picture in MPEG2 format is the following. First, the header information and the start code are removed from the bitstream. Next, the pure data information is decoded by a variable length decoder (VLD). The pixel value of the original picture is restored through an inverse quantization process and an inverse discrete cosine transformation process. With the syntax defined by MPEG2, the header information and the start code are removed from the bitstream and the pure data information is decoded by the VLD.
An example of the VLD function can be found in U.S. Pat. No. 5,173,695. Generally, the syntax of MPEG2 video (ISO/IEC 13818-2) includes variable length codes and conditional sentences. Therefore, a complicated state machine (with, for example, many registers) and many shift operations are needed for parsing variable length codes and conditional sentences.
If the state machine above is hardwired, then the complexity of the hardware is much higher and parsing speed isn't increased because of the corresponding increase in gate stages.
A general purpose processor, such as a digital signal processor or central processing unit, is overkill for the syntax parser because the syntax parser is typically only used for parsing MPEG video.